Control apparatus for hammer type impact printer

ABSTRACT

An alterable storage unit is included in a control apparatus to store code conversion tables for transforming type data or type position data into various control data such as a hammer pressure, an amount of ribbon feed and an amount of proportional space. When a type element is replaced with another, code conversion tables concerned with the new type element are stored in the storage unit. This permits the code conversion tables to be altered or renewed concentratedly in the event of type element replacement.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. Patent application Ser. No.745,750, filed June 17, 1985, now U.S. Pat. No. 4,627,751, issued Dec.9, 1986, which is a continuation of U.S. Patent application Ser. No.404,799, filed Aug. 3, 1982, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a control apparatus for an impactprinter for use with various computer systems or word processors andprovided with a set of interchageable type elements, which may be in theform of type wheels, for printing using different respective characterfonts.

In an impact printer of the type described, printing operation iscontrolled based on various control data matching with the kind, font,size and other factors of type members, such as hammer pressure, amountof ribbon feed and amount of space, for the purpose of reproducing datawhich are readily identifiable. Since characters are available in upperand lower cases, hammering all the types with a same pressure wouldrender the lower case letters denser than the upper case letters. Inlight of this, the hammer pressure is varied depending on the size of acharacter so that all the characters printed out will have a uniformdensity. Meanwhile, where use is made of a multistrike ribbon which canserve 3-5 times of repeated use throughout its length, some charactersmay each become uneven in density due to the repeated printing actionsin each region of the ribbon. To ensure an even density over eachcharacter, the amount of ribbon feed is varied from one type to another.Also, should types be hammered at a predetermined intercharacterspacing, the reproduced characters would appear spaced differentdistances due to different widths of characters which might causeadjacent characters to overlap or be spaced too much. The intercharacterdistance of reproduced data is usually controlled to predetermined oneby varying the amount of space depending on the width of a type. Itshould be noted that the amount of space matching with the width of aspecific type is referred to as a "proportional amount of space".

A known expedient for such a print control employs a read only memory orROM which stores as code conversion tables the control data such ashammer pressures, amounts of ribbon feed and those of proportionalspaces which correspond to type data using ASCII codes or JIS codes, forexample, or type position data provided by converting the type data.During a print control operation, the code conversion tables areconverted into hammer pressures, ribbon feeds and proportional spaces inresponse to input type data.

Meanwhile, some impact printers of the type described are furnished witha plurality of different kinds of interchangeable type wheels to win awider range of applications. The type wheels may carry 88, 94, 96 and128 type elements, respectively. Replacing the type wheel with anothercan change the kind of types, font, size etc.

In a printer with such interchangeable type wheels, the carriage ismovable up and down relative to the printer body to facilitate thereplacement of the type wheel which is loaded on the carriage. Thecarriage lacks grips for manipulation and usually raised with anupwardly extending hammer section held by hand, for instance. This isundesirable, however, because such a functional part of the carriage hasbeen assembled by very delicate positioning. While this problem may besettled if suitable grips are mounted on the carriage independently ofthe other structural parts, such cannot be accomodated from theviewpoint of space requirement due to the highly compacted constructioninherent in this type of products.

It is an object of the present invention to provide a control apparatusfor a hammer type impact printer which permits the use of a plurality ofdifferent kinds of interchangeable type elements and promotes sure andeasy replacement.

It is another object of the present invention to provide a controlapparatus for a hammer type impact printer which when a type element isreplaced with another, a print control can be effected merely byentering type data but not control data and, thereby, minimizes theintricacy of data processing procedure as well as the data transfer timeto the printer.

It is another object of the present invention to provide a controlapparatus for a hammer type impact printer which enhances theconvenience of operation of the printer by providing a display of thekind of a specific type element to be replaced.

It is another object of the present invention to provide a controlapparatus for a hammer type impact printer which allows one to grip thecarriage for the replacement of a type element without requiring anyadditional space.

It is another object of the present invention to provide a generallyimproved control apparatus for a hammer type impact printer.

Other objects, together with the foregoing, are attained in theembodiments described in the following description and illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing a hammer type impactprinter to which the present invention is applicable;

FIG. 2 is a side elevation of a carriage locking mechanism included inthe printer shown in FIG. 1;

FIG. 3 is a front view of a modification to the mechanism shown in FIG.2;

FIG. 4 is a front view of a mechanism for shifting a type wheel to upperand lower positions for the selection of a type on a type wheel;

FIG. 5 shows a data pattern conventionally inputted in a printer afterthe replacement of a type element;

FIG. 6 illustrates how FIGS. 6a and 6b are combined to constitute ablock diagram of a control apparatus for a hammer type impact printerembodying the present invention;

FIGS. 7 and 8 show different examples of input data which will betransferred to the printer to alter tables when a type element isreplaced;

FIG. 9 illustrates how FIGS. 9a, 9b, 9c and 9d are combined toconstitute a flowchart of a printer control which the control apparatusshown in FIG. 6 practices;

FIG. 10 is a flowchart indicating an example of a subroutine for thetable renewal shown in FIG. 9;

FIG. 11 is a flowchart showing another example of the subroutine for thetable renewal of FIG. 9;

FIG. 12 is a block diagram showing an example of a prior art wordprocessor; and

FIG. 13 is a block diagram showing another embodiment of the hammer typeimpact printer of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the control apparatus for a hammer type impact printer of thepresent invention is susceptible of numerous physical embodiments,depending upon the environment and requirements of use, substantialnumbers of the herein shown and described embodiments have been made,tested and used, and all have performed in an eminently satisfactorymanner.

Reference will first be made to FIGS. 1-4 for describing in detailmechanisms of a hammer type impact printer to which the presentinvention is applicable.

Referring to FIG. 1, a carrier 10 in the form of a diecasting or thelike is reciprocatable on and along a pair of parallel guide rods (notshown). The carrier 10 is formed with a V-shaped upwardly open recess 12and a flat surface 14 at each of its laterally opposite ends. The flatsurface 14 is provided with a positioning pin 16 and a threaded opening18. A generally channel-shaped presser plate 20 is formed with anelongate slot 22 and laid on each flat surface 14 so that thepositioning pin 16 is received in the slot 22. A small screw 24 isthreaded into the opening 18 through the slot 22 to fix the presserplate 20 in a desired position. These elements at each lateral end ofthe carrier 10 constitute a carriage mounting section 26 which is spaceda predetermined distance from and laterally aligned with the one locatedat the other lateral end.

A carriage locking mechanism 28 is arranged on a front part of thecarrier 10. The carriage locking mechanism 28 includes a base plate 36rigidly mounted on the carrier 10 and having a reference lug 32 whichextends upright to define a vertical reference surface 30. A retainingsurface 34 also extends upright from the base plate 36 while beingoffset from the reference lug 32 by an amount equal to a thickness ofthe base plate 36. Guide pins 38 and 40, one of which is longer than theother, extend horizontally from the retaining surface 34. A lockermember 44 is formed with an elongate recess 42 and slidable horizontallywith the guide pins 38 and 40 received in its slot 42. The locker memberor slider 44 is prevented from slipping out of the guide pins 38 and 40by stop rings 46 which are secured to the guide pins. The laterallyoutermost end of the locker member 44 is bent to have a hook 48. Atension spring 50 is anchored at one end to the hook 48 and at the otherend to the guide pin 38 so that the slider 44 is constantly biasedtoward the reference lug 32. The slider 44 is provided with convergingupper and lower inclined edges 52 and 54 at the other end.

A carriage is generally designated by the reference numeral 56 andincludes a body 58 which may be a die-casting. Pins 60 extendhorizontally away from each other at the laterally opposite ends of thebody 58. Rollers 62 are free to rotate on the respective pins 60 butprevented from axial movement. A pin 64 is studded on the front end ofthe body 58 in an intermediate lower portion of the latter. A driveshaft 68 extends from the center of the front end of the body 58 toremovably carry a type wheel 66 thereon. A hammer 72 is movable towardand away from the type wheel 66 on a projection 70 of the body 58 abovethe drive shaft 68. Located to the rear of the hammer 72 is an armature74 which is operated by a magnet (not shown).

A pair of ribbon guides 80 each in the form of a shaped plate arefastened to the body 58 by small screws 82 and 84 at opposite sides ofthe projection 70, more specifically at each side wall 76 of theprojection 70 and a flat surface 78 which extends from the side wall 76.Each of the ribbon guides 80 is formed with a horizontal surface 86, avertical tongue 88 extending from the front end of the horizontalsurface 86 to position a ribbon cassette as will be described, anupwardly inclined surface 90 contiguous with the horizontal surface 86,and a vertical surface 92 contiguous with the inclined surface 90. Thefront edges of the contiguous surfaces 90 and 92 are finished smoothlyto serve as a guide surface 94 for a ribbon. The vertical surface 92carries in its intermediate portion a piece of plastic 96 to form a gripsection 98. The grip section 98 thus positioned at the opposite sides ofthe hammer 72 prevents one from directly holding the hammer 72.

Disposed to the rear of the carriage 56 is a ribbon cartridge mountingsection which is generally designated by the reference numeral 100. Thesection 100 comprises a support plate 102 which is rigidly mounted tothe body 58 of the carriage 56. A ribbon feed shaft 104 is carried onone side of the support plate 102 to be driven by a motor (not shown).Upright tongues 106 extend from opposite outermost edges of the supportplate 102 while retainer pins 108 extend toward each other from therespective tongues 106. A retainer block of elastic plastic 110 isrotatably mounted on each of the retainer pins 108. As shown, eachretainer block 110 has a base portion 112 receiving a retainer pin 108therein, a leg 114 extending in longitudinally opposite directions fromthe base portion 112, and an upwardly extending pawl 116. Projections118 extend upwardly from both ends of the top of the leg 114. Theuppermost end of each pawl 116 is bent outwardly to form a lug 120 whichwill be depressed to release a ribbon cartridge. The retainer blocks 110are individually biased by a tension spring (not shown) such that theirfront ends face downward.

A ribbon cartridge 122 is removably mounted on the carriage 56. Theribbon cartridge 122 comprises a casing 124 of plastics which stores anendless printing ribbon 126 thereinside. Outside the casing 124, theribbon 126 spans a pair of leg portions 128 which individually extendforwardly from the casing 124. A shaft 130 is rotatably mounted on thelower end of the casing 124 and provided with a portion which isengagable with the ribbon feed shaft 104, though not shown in thedrawing. The shaft 130 can also be rotated by hand whenever required. Ateach side of the casing 124, there are formed a horizontal lug 132engagable with corresponding one of the pawls 116 of the retainer block110, and shoulders 134 located at longitudinally opposite sides of thelug 132 to face both sides of the pawl 116 for thereby keeping thecartridge 122 from longitudinal movement relative to the carriage 56.

Denoted by the reference numeral 136 are pins each being adapted to beconnected with a wire (not shown) for driving the carrier 10.

To load the ribbon cartridge 122 on the carriage 56, the former ispressed downwardly with its opposite lugs 132 aligned with the oppositepawls 116 of the cartridge mounting sections 110. Then, the lugs 132urge the corresponding pawls 116 away from each other due to theinclined tops of the latter until the pawls 116 spring back into contactwith the lugs 132. Each pawl 116 becomes positioned between thecorresponding shoulders 134 to positively retain the cartridge 122 inposition. The tongues 88 of the ribbon guides 80 facilitate positioningof the ribbon cartridge 122.

In this situation, the ribbon 126 engaged with the guide surfaces 94 isin a lowered position because the retainer blocks 110 have faceddownward at their front ends as previously mentioned. When a raisingmechanism (not shown) is activated, the ribbon cartridge 122 will berotated together with the retainer blocks 110 to bring the ribbon 126 toits raised position. It will be seen that such a movement of the ribboncartridge 122 is quite smooth and accompanied by no vibration or thelike because the massive support plate 102 is fixed in place. Anadditional retaining effort will be offered by the legs 114 of theretainer blocks 110 which bend themselves when the pawls 116 lock theribbon cartridge 122.

Depressing the opposite lugs 120 downwardly will cause the pawls 116 tomove away from each other so that one can readily remove the ribboncartridge 122 out of the carriage 56.

To replace the type wheel 66 with another, the grip sections 98 of theribbon guides 80 are held by hand and moved upwardly. Then, the pin 64on the body 58 exerts an upward force on the lower inclined edge 54 ofthe slider 44 so that the slider 44 is pushed transversely against theforce of the spring 50, until the pin 64 moves clear of the carriagelocking mechanism 28. This allows the whole carriage 56 to be angularlyraised about the horizontal pins 60 to a predetermined position asindicated by a phantom line in FIG. 2. In this instant, the pins 60rotate relative to their associated rollers 62 which have been firmlyretained by the presser plates 20 on the carrier 10. The type wheel 66can now be replaced by another without being disturbed by anysurrounding member such as a platen (not shown). The carriage 56 can bereset on the carrier by simply pressing it downwardly, opposite to theabove-mentioned procedure, to a position indicated by a solid line inFIG. 2. This time, the pin 64 abuts against the upper inclined edge 52of the slider 44 to move it transversely. After the pin 64 has moveddownward past the slider, the latter springs backs into retainingcontact with the pin 64 at its lower inclined edge 54.

It will be seen that the carriage 56 can be moved up and down withoutany danger due to the grip sections 98 which keep operator's hands clearof the hammer 72.

The inherent construction and arrangement of the present inventionpermits the carriage 56 to be removed from the carrier 10. When thescrews 26 are loosened to move the presser plates 22 to the rear, theV-shaped recesses 14 become uncovered so that the rollers 62 can beraised out of the recesses 14. To attach the carriage 56 to the carrier10, on the other hand, the rollers 62 are placed in the V-shapedrecesses 14 and the pin 64 is locked in the carriage locking mechanism28 in the manner described, while maintaining the carriage 56transversely movable. Then, the pin 64 is positioned in the transversedirection by the reference surface 30 and inclined edge 54 of themechanism 28. Under this condition, fastening the presser plates 22 tothe carrier 10 by the screws 26 with the rollers 62 held therebetweenpositions the carriage 56 relative to the carrier 10. The carriage 56thus positioned will not be dislocated thereafter relative to thecarrier 10 due to the axially fixed positions of the rollers 62 andtheir associated horizontal pins 60.

FIG. 3 shows a modification to the carriage locking mechanism 28 andwhich is characterized in that the lower inclined edge 54 of the slider44 terminates at a flat edge 138 at its upper end. In case where thetype wheel 66 carries two trains of type elements in concentricpositions, and is movable to two steps during printing operations, theflat surface 138 will prove effective to prevent the carriage 56 fromjumping to an excessive level. Naturally, manually moving the carriage56 upwardly will be resisted by a temporary increase of load whichaffords a favorable sense of clicking.

FIG. 4 illustrates a mechanism which constitutes means for rendering thecarriage 56 shiftable to two steps as mentioned above during printingoperations. An armature 142 is pivotable about a shaft 140 which isfixed to the carrier 10. The armature 142 retains the drive shaft 68 atits free end. A leaf spring 144 is fixed at one end and fitted at theother end to the armature 142. Magnets 146 and 148 face the armature 142from vertically opposite sides, respectively. During the course ofprinting actions, either the upper magnet 146 or the lower magnet 148 isenergized to raise or lower the type wheel 66. Because the biasing forceof the leaf spring 144 acts only in the linear manner, the leaf spring144 will be well balanced during its upward or downward movement ifprovided with a relatively small spring constant and directed to aneutral position. It will be apparent that the "neutral position"implies not a dimensionally neutral position but an essential neutralpoint of motion with the weight of the carriage 56 also taken intoconsideration.

When a type wheel of such a hammer type impact printer is replaced byanother, the hammer pressure, the amount of ribbon feed and the amountof proportional space will be controlled in a manner described in detailhereunder.

A prior art control of such factors is represented in FIG. 5. As alreadydiscussed, it has been customary to store in a read only memory codeconversion tables for providing control data on only a standard typewheel of most frequent use; once the standard type wheel is replaced,the code conversion tables cannot be used any longer. This has beencoped with by entering alternative control data on one type into theprinter together with data on the type, as indicated in FIG. 5. In FIG.5, the first byte represents the alphabet "A" in ASCII code while thesecond byte represents an exemplary pattern of control data on thealphabet "A". The data pattern illustrated comprises a parity bit PB,hammer pressure HF, ribbon feed RF and proportional space PS.

As previously pointed out, entering new control data every time data onone type is entered requires the printer to be controlled in anintricate way due to the additional amount of input data. This slowsdown the data transfer to the printer.

Referring now to FIG. 6, a printer control apparatus embodying thepresent invention is shown. Data DT is sequentially fed to the controlapparatus from a microcomputer or the like installed in a dataprocessing system (not show) with which the printer is associated. Thedata DT is once accumulated in a buffer 150 and inputted in adiscriminator circuit 152. The data DT has eight bits which may beallotted, for example, to indicate a type to be selected (type data), aspacing operation for space of one character, a line feeding operationfor incrementaly feeding a sheet vertically, a carriage returningoperation for returning the carriage to a home position, a tablealtering or renewing operation, a hammer pressure, a ribbon feed and aproportional space.

In this embodiment, the input data DT uses ASCII codes while aninstruction for a table renewal is provided by sequentially transferring"ESC" code and "+" code.

The discriminator circuit 152 identifies the content of the input dataDT. If the data DT is an operation command commanding printing, spacing,line feed or carriage return, the discriminator 152 supplies a drivesequence control circuit 154 with an operation command signal PD, SD, LDor CD. In response to a print command, the discriminator 152 deliverstype code input data DT to a wheel position table 158 of a memory 156.Further, in response to a table renewal command, the discriminator 152supplies a table renewal control circuit 160 with a control signal CSand the input data DT.

The memory 156 is made up of a read only memory or ROM and a renewablestorage means or in the form of RAM. The wheel position table 158 is acode conversion table adapted to convert a type code into type positiondata of the type wheel and stored in advance in the ROM. The wheelposition table 158 feeds type position data PDD corresponding to theinput type code input data DT to a hammer pressure table 162, a ribbonfeed table 164, a proportional space table 166 and a type selectioncontrol circuit 168, which will be described later.

Stored individually in the ROM or the RAM, the hammer pressure table162, ribbon feed table 164, and proportional space table 166 are thecode conversion tables for transforming the type position data PDD fromthe wheel position table 158 into a hammer pressure, a ribbon feed, anda proportional space, respectively.

Thus, in accordance with this embodiment, a code conversion tablecorresponding to a standard type wheel in stored in the ROM as fixeddata, while when the standard type wheel is replaced with another typewheel, a code conversion table corresponding to the new type wheel willbe stored in the RAM.

The hammer pressure table 162, ribbon feed table 165 and proportionalspace table 166 supply a hammer control circuit 169, a ribbon feedcontrol circuit 170 and a carriage control circuit 172 with hammerpressure data HMD, ribbon feed data RFD and proportional space data PSD,respectively, each of which corresponds to the type position data PDD.

In response to the control signal CS from the discriminator 152, thetable renewal control circuit 160 starts a renewal control on each ofthe tables 162, 164 and 166 whereby a hammer pressure, a ribbon feed anda proportional space corresponding to a type indicated by the input dataDT are stored in the RAM as code conversion tables. After the renewal oftables, the table renewal control 160 operates such that the typeposition data PDD from the wheel position table 158 is entered into theRAM instead of the ROM. Details of such a procedure will be describedlater.

The drive sequence control circuit 154, in response to an operationcommand signal PD, SD, LD or CD from the discriminator 152, controls thehammer control 169, ribbon feed control 170, carriage control 172 orline feed control 174 to practice the operation instructed by thecommand signal.

The type selection control circuit 168 responds to the wheel positiondata PDD from the wheel position table 158 to control a type selectiondrive circuit 176, so that a type drive motor 178 is driven to rotatethe type wheel 66 until a desired type reaches a predetermined impactposition.

The hammer control circuit 169, based on the hammer pressure data HMDfrom the hammer pressure table 162, controls a hammer drive circuit 180to drive a hammer magnet 182. Then, the hammer 72 will hit against aselected type of the type wheel 66 with a necessary pressure so as toprint out data.

The ribbon feed control circuit 170 supplied with the ribbon feed dataRFD from the ribbon feed table 164 controls a ribbon feed drive circuit184 so that a ribbon feed motor 186 is driven to move the ribbon 126 anecessary distance.

The carriage control circuit 172, in response to the proportional spacedata PSD from the proportional space table 166, controls a carriagedrive circuit 188 to drive a carriage motor 190 until the carriage 56moves a necessary proportional space. For a spacing operation, thecarriage 56 will be moved a predetermined amount of space.

The line feed control circuit 174 is adapted to control a line feeddrive circuit 192 such that a line feed motor 194 is driven to feed asheet an incremental one line.

Referring to FIGS. 7 and 8, there will be described input data DT whichwill be transferred from the data processing system to the printercontrol apparatus for practicing a data renewing operation when the typewheel on the carriage is changed from standard one to another.

FIG. 7 shows an example of input data DT arranged to alter the controldata for all the types of a type wheel. The data DT has the first bytefor ASCII code ("0011011") and the second byte for "+" code ("0101011")which are transferred in succession. Thereafter, from the third byte andonward, hammer pressures (HP), ribbon feeds (RF) and proportional spaces(PS) for all the types on a type wheel are transferred sequentially inthe order or type positions (type addresses) or the order of types to bewritten in the code conversion tables. The number of type elements are"94" by way of example in FIG. 7.

FIG. 8, on the other hand, indicates an example of input data DT foraltering the control data on a part of the type elements of a typewheel. In the first and second bytes, "ESC" code are transferredsequentially. In the third byte and onward, a type code indicating atype element whose control data should be renewed and data on its hammerpressure (HP), ribbon feed (RF) and proportional space (PS) aretransferred in succession, followed by another set of such code and dataif any. At the end of the renewal, "ESC" code is transferred. In FIG. 8,the third byte "1000001" is code data indicating the alphabet "A" andthe fifth byte "1100001" code data, indicating the alphabet "a".

Reference will be made to FIGS. 9-11 for describing the printingoperation and the table renewing operation which the printer controlapparatus will practice.

At STEPS 1 and 2 in FIG. 9, whether or not unprocessed data is presentin the buffer 150 is checked and, if YES, input data DT is inputted inthe discriminator 152 while the buffer 150 is cleared. At STEP 3, thediscriminator 152 determines whether or not the input data is a typecode and, if YES, STEPS 4-15 are performed sequentially to print outdata. If NO, the operation proceeds to STEP 16 which will be described.At STEP 4, the type code input data DT is transformed by the wheelposition table 158 into type position data PDD. At STEP 5, whether thetable referred to is the ROM or not is determined and, if YES, STEP 6 iscarried out but, if NO, then STEP 9. Stated another way, it isdetermined which one of the tables 162, 164 and 166 stored in ROM andthe tables 162, 164 and 166 stored in RAM should be used as codeconversion tables for converting the type position data PDD into ahammer pressure, a ribbon feed and a proportional space.

At STEPS 6-8, with reference to the hammer pressure table 162, ribbonfeed table 164 and proportional space table 166 stored in the ROM, thetype position data PDD is transformed into hammer pressure data HMD,ribbon feed data RFD and proportional space data PSD. At STEPS 9-11, thetype position data PDD is transformed into hammer pressure data HMD,ribbon feed data RFD and proportional space data PSD with reference tothe hammer pressure table 162, ribbon feed table 164 and proportionaltable 166 stored in the RAM. At STEPS 12-15, the drive sequence controlcircuit 154 sequentially drives the type selection control 168, hammercontrol 169, ribbon feed control 170 and carriage control 172. Then, thetype indicated by the type position data PDD is brought to the impactposition, the hammer 72 is driven to hammer the type with the pressureindicated by the hammer pressure data HMD, the ink ribbon 126 is fed byan amount indicated by the ribbon feed data RFD, and the carriage 56 ismoved a distance indicated by the proportional space data PSD. Theprinting action terminates here and returns to STEP 1. In this way, theprinter can be controlled during printing operations merely by enteringtype data as the input data DT. At STEP 16, the discriminator 152determines whether the input data DT is "ESC" code or not and, if YES,STEP 17 is performed but, if NOT, the operation jumps to a functionroutine such as a line feed operation (LF) or a carriage returnoperation (CR). At STEPS 17 and 18, whether or not input data DT isstored in the buffer 150 is checked and, if YES, it is entered with thebuffer 150 cleared. At STEPS 19 and 20, the discriminator 152 determineswhether the input data is "+" code or not, and, if YES, the operationreturns to STEP 1 after the table renewal but, if NOT, the operationjumps to a special function routine.

Referring to FIGS. 10 and 11, other examples of the table renewingsubroutine will be described with reference to FIG. 9. FIG. 10represents a case wherein input data DT is transferred in the manner ofFIG. 7 while FIG. 11 represents a case wherein input data DT istransferred in the manner of FIG. 8.

At STEPS 21 and 22 in FIG. 10, whether or not input data DT is presentin the buffer 150 is checked. If YES, the data DT is entered and thebuffer 150 is cleared; the discriminator 152 transfers the input data DTto the table renewal control 160. At STEPS 23 and 24, the table renewalcontrol 160 sets in RAM hammer pressures, ribbon feeds and proportionalspaces concerning all the 94 types in the order of type positions or oftypes to be written in the code conversion tables. Thus stored in theRAM are the code conversion tables corresponding to a specific typewheel 66 mounted on the carriage, i.e. hammer pressure table 162, ribbonfeed table 164 and proportional space table 166. At STEP 25, the tablerenewal control 160 is operated to switch the tables to be referred tofrom those stored in the ROM to those stored in the RAM. This conditionsthe RAM to receive type position data PDD from the wheel position table158.

In FIG. 11, at STEP 26, all the data of the hammer pressure table 162,ribbon feed table 164 and proportional space table 166 stored in ROM areshifted to RAM. At STEPS 27 and 28, whether or not input data DT ispresent in the buffer 150 is checked. If YES, it is entered with thebuffer 150 cleared and the data is transferred to the table renewalcontrol 160. At STEPS 29 and 30, of all the data shifted from the ROM tothe RAM by the table renewal control 160, the hammer pressure, ribbonfeed and proportional space data are altered only for a type code whichhas been delivered as input data DT. Thus, the RAM stores a hammerpressure table 162, a ribbon feed table 164 and a proportional spacetable 166 each corresponding to the new type wheel loaded on thecarriage. It will be seen that in the example shown in FIG. 8 thecontrol data are renewed only for the types "A" ("1000001") and "a"("1100001"). Finally, in STEP 31, the reference tables are changed fromthose in the ROM to those in the RAM.

By the above procedure, when the type wheel on the carriage is replaced,various control data corresponding to a new type wheel are transferredconcentratedly from the data processing system to the printer so thatthe RAM stores code conversion tables corresponding to the new typewheel.

The various control data on type wheels may be stored in suitable memorymeans such as a floppy disc or a paper tape so that the stored data canbe read and transferred to the printer when the type wheel is replaced.

Also, the RAM for storing code conversion tables may be constituted by acore memory, a bubble memory, a floppy disc or IC memory, for example.

While the present invention has been shown and described as employing atype wheel having 94 type members in total, it will be seen that it isapplicable in the same manner to a type wheel having 128 type members, atype element in the form of a ball, etc.

Though the embodiment has used ASCII codes, use of any other specialcodes such as JIS codes will not affect the principle of the presentinvention at all.

The embodiment has employed ROM for storing code conversion tables asfixed data, in addition to RAM. This is not restrictive in any way; codeconversion tables may be stored in RAM only. Furthermore, an arrangementmay be made such that only the code conversion table for ribbon feeds isstored in ROM as data which is unrenewable, instead of storing all theconversion tables in RAM.

Thus, in accordance with embodiment described hereabove, various controldata concerning any kind of type element mounted on the carriage can betransferred altogether to the printer so that the code conversion tablesare replaced with those corresponding to the specific type element. Thetime period necessary for the replacement of the code conversion tablesis negligibly short. Accordingly, when the type element is replaced withanother, type data need only be entered from the data processing systemto the printer during a print control. This avoids intricacy of dataprocessing operation required for printer control as well as an increaseof data transfer time.

Referring to FIGS. 12 and 13, another embodiment of the presentinvention is shown which is designed to selectively use a limited numberof ROM corresponding to the number of type wheels usable for a printerand each storing code conversion tables for each type wheel as fixeddata, in place of the renewable storage means (RAM) mentioned in thefirst embodiment. This kind of design will be desirable where the numberof interchangeable type wheels is relatively small, such as two tothree.

For the convenience of description, the embodiment shown in FIGS. 12 and13 is supposed to be related with a printer associated with a wordprocessor and having two kinds of interchangeable type wheels, i.e. amost frequently used type wheel with standard type members and a specialtype wheel with symbols for scientific expression.

Referring to FIG. 12, a conventional word processor comprises a keyboard200, a data buffer 202, a 1-line display 204, a printer 206 using typewheels, and an outside storage device 208. The data buffer 202 isadapted to store data entered through the keyboard 200 or data read fromthe outside storage device 208. The 1-line display 204 displays the datastored in the data buffer 202 line by line while the printer 206 printsout the same data one line at a time. The outside storage device 208 inthe form of a floppy disc, for example, is used to store the data in thedata buffer 202. Alphanumeric characters or like code data enteredthrough the keyboard 200 are displayed successively on a cursor whichindicates an input position on the 1-line display 204. After one line ofdata has been entered, the content of the data buffer 202 is transferredto the outside storage device 208 just before it overflows.Alternatively, the content of the data buffer 202 may be coupled to theprinter 206 to be printed out. Data can be added, omitted or correctedby operating a cursor control key on the keyboard 200 until the cursorreaches a desired position on the display.

Referring to FIG. 13, the data buffer 202 has a first buffer area a anda second buffer area b. The printer control apparatus also includes aninput code discriminator circuit 210, a print buffer 212, a print outputcontrol circuit 214 and a print table assembly 216 storing printercontrol data and made up of a table I for the standard type wheel and atable II for the special type wheel for scientific expression. Alsoincluded in the printer control apparatus are a data buffer controlcircuit 218, a display buffer 220, a message table 222 and a characterpattern memory 224 having a memory area I for the standard type wheeland a memory area II for the special type wheel. Further included in theprinter control apparatus are a latch and decoder 226 for wheel changedata, AND gates G₁ -G₄ and OR gates G₅ and G₆. Text data DT' is coupledfrom the input code discriminator 210 the OR gate G₆. Wheel changecontrol codes WE₁ and WE₂ are delivered from key input means when wheelchange keys K_(I) and K_(II) are manipulated, respectively. In responseto the wheel replacement control code WE₁ or WE₂, the latch and decoder226 produces a gate switch signal SA or SB. The data buffer control 218delivers a signal SC when the cursor and the wheel change control codecoincides with each other. The OR gate G₅ produces an output signal SG₅.

The printer control circuit shown in FIG. 13 differs from conventionalone in the following various respects.

(1) The keyboard 200 shown in FIG. 12 is additionally provided with thewheel change keys K_(I) and K_(II) for indicating the selection of thestandard and special type wheels, respectively. Accordingly, when theinput code discriminator 210 is supplied with the wheel change controlcode WE₁ or WE₂ corresponding to the key K_(I) or K_(II), it deliversthe code as a control code.

(2) The latch and decoder 226 is employed for holding wheel change dataand producing the signal SA or SB which corresponds to the kind of aspecific type wheel.

(3) The print table assembly 216 is made up of the table I correspondingto the standard type wheel and the table II corresponding to the specialtype wheel.

(4) The character pattern memory 224 has the memory area I for storingcharacter pattern data on the standard type wheel and the memory area IIfor storing character pattern data on the special type wheel.

(5) The AND gates G₁ and G₂ are associated with the print tables 216 inorder to switch the tables I and II from one to the other.

(6) The character pattern memory 224 is provided with the AND gates G₃and G₄ which switch the memory areas I and II from one to the other.

(7) The message table 222 stores messages indicating type wheel changesand the kinds of type wheels.

These differences will be described in more detail later. The rest ofthe circuit is similar to the control circuit of a prior art wordprocessor.

The blocks of FIG. 13 common to those of the prior art word processorwill be outlined hereunder.

The input code discriminator 210 determines whether the key input is thetext data or the function data. The data buffer 202 stores in the firstbuffer area a the data appearing on the display 204 before the cursorposition and, in the second buffer area b, the data after the cursorposition. The print buffer 212 is loaded with one line of data when oneline of data has been shifted to the first buffer area a of the databuffer 202, that is, when the cursor on the display 204 has detected aline change code. The print output control 214 processes the content ofthe print buffer 212 and feeds it to the printer. The print tableassembly 216, as previously mentioned, is made up of the table I for thestandard type wheel and the table II for the special type wheel.

In a printer associated with a word processor, as well as others,various delicate controls are required such as producing a variableintercharacter spacing (proportional printing), adjusting the interwordspacing to vertically align the ends of lines (justification), andcontrolling the printing pressure of each character, different fromordinary printers which print out the content of the print buffer 212simply at fixed pitches. Therefore, there must be prepared adisplacement table, a print pressure table and other tablescorresponding to respective character codes. Specific tables are used inaccordance with the font on a type wheel or the kind of characters on atype wheel. The print tables 216 store such groups of tables which willbe referred to in correspondence with the codes in the print buffer 212.

The data buffer control 218 loads the display buffer 220 with the datastored in the data buffer 202 one line at a time. The transfer of datato the display buffer 220 will occur when a character key is depressed,the cursor control key is depressed, a message as operation guidance isdisplayed, or the like. The message table 222 stores various messagesfor operation guidance. The character pattern memory 224 stores data ofcharacter patterns to be displaced on the display 204.

Now, of the additional provisions (1)-(7) in accordance with thisembodiment, (1), (3) and (4) have already been discussed and, therefore,the following description will concentrate to (2) concerned with thelatch and decoder 226, (5) and (6) concerned with the gates G₁ -G₄ and(7) concerned with the message table 222.

The latch and decoder 226 comprises a register for latching wheelreplacement data and a decoder for decoding the replacement data. Thelatch and decoder 226 is supplied with a signal SG₅ which the OR gate G₅delivers in response to the wheel change control code WE₁ or WE₂ whichin turn appears when the wheel change key K_(I) or K_(II) is operated.The latch and decoder 226 produces a gate switch signal SA in responseto the control code WE₁ and a gate switch signal SB in response to thecontrol code WE₂. In response to the wheel change control code WE₁, thesignal SA becomes logical "1" and the signal SB logical "0"; in responseto the control code WE₂, the signal SA becomes logical "0" and thesignal SB logical "1".

Such gate switch signals SA and SB are coupled to the AND gates G₁ -G₄as have been described in the items (5) and (6). Accordingly, when thewheel change key K_(I) designating the standard type wheel is selected,the wheel change control code WE₁ is generated to make the gate switchsignal SA logical "1" thereby opening the gates G₁ and G₃. Of the printtables 216, the table I corresponding to the standard type wheel is madeeffective by the AND gate G₁. Likewise, the memory area I of thecharacter pattern memory 224 storing the pattern data of the standardtype wheel is made effective by the AND gate G₃.

When the other key K_(II) designating the special type wheel ismanipulated, the wheel change control code WE₂ appears to render thegate switch signal SB logical "1" which causes the gates G₂ and G₄ toopen. Then, the table II of the print tables 216 corresponding to thespecial type wheel is made effective by the AND gate G₂ while the memoryarea II of the character pattern memory 224 storing the pattern data ofthe special type wheel is made effective by the AND gate G₄.

The message table 222 stores messages indicating changes of type wheeland the kinds of type wheels. The messages may be, for example, "WHEELCHANGE : STANDARD" to indicate the standard type wheel and "WHEEL CHANGE: SCIENTIFIC" to indicate the special type wheel. Data in the messagetable 222 is coupled to the display buffer 220 when the data buffercontrol 218 has been operated by the output signal SB₅ of the OR gateG₅, which receives the wheel change control code WE₁ or WE₂. In theevent the final document is to be prepared, the data delivery from themessage table 222 to the display buffer 220 occurs in response to thesignal which appears upon coincidence of the cursor with the controlcode WE₁ or WE₂.

In operation, suppose that the wheel change key K_(I) on the keyboard200 has been selected to use the standard type wheel. Then, the inputcode discriminator 210 delivers a wheel change control code WE₁ which isstored in the first buffer area a of the data buffer memory 202 via theOR gate G₆. At the same time, the code WE₁ is passed through the OR gateG₅ and coupled to the latch and decoder 226 as a gate output SG₅,whereby the logical "1" gate switch signal SA is coupled to the ANDgates G₁ and G₃. This makes the table I of the print tables 216 and thememory area I of the character pattern memory 224 effective, each ofwhich corresponds to the standard type wheel.

Simultaneously, the output SG₅ of the OR gate G₅ is supplied to the databuffer control 218 as a wheel change request signal. The content of thedisplay buffer 220 is switched from the data buffer 202 to the messagetable 222, whereby the display buffer 220 produces a messagecorresponding to the wheel change control code WE₁ which designates thestandard type wheel. The 1-line display 204 now displays the message"WHEEL CHANGE : STANDARD" designating the standard type wheel.

In view of the very frequent use of a standard wheel for ordinaryapplications, such an arrangement is permissible that every time theword processor starts to prepare a text, the wheel change control codeWE₁ is automatically delivered to initialize the word processoraccordingly.

The operator looking at the 1-line display 204 replaces the type wheelif not the standard type wheel and, then, operates a reset key on thekeyboard. The reset key cancels the message on the 1-line display 204and allows the content of the data buffer 202 to appear instead. Underthis condition, preparation of a text is started.

When the key input is the text data DT', the data is sequentially fedfrom the OR gate G₆ to the data buffer 202. Every time one line of datais fully loaded in the data buffer 202, it is printed out by the printer206 while being shifted to the outside storage device 208. Accordingly,the file stored in the outside storage device 208 has the wheel changecontrol code WE₁ at its head and text data after the control code WE₁.

Suppose that a need for symbols for scientific applications has arisedwhile the text is prepared by the standard type wheel. In this instance,the wheel change key K_(II) at the keyboard 200 is depressed and theinput code discriminator 210 discriminates a code of the wheel changekey K_(II). This code is stored in the first buffer area a of the databuffer 202 as a wheel change control code WE₂ and, at the same time,coupled to the latch and decoder 226 via the OR gate G₅ by the gateoutput SG₅. This makes the gate switch signal SB logical "1" and thegate switch signal SA logical "0", so that the table II of the printtable assembly 216 and the memory area II of the character patternmemory 224 are individually rendered effective.

At the same time, the output SG₅ of the OR gate G₅ is coupled to thedata buffer control 218 as a wheel change request. The content of thedata buffer 202 is then switched from the data buffer 202 to the messagetable 222. As a result, the message on the display 204 is changed from"WHEEL CHANGE : STANDARD" to "WHEEL CHANGE : SCIENTIFIC" based on thecontent of the text. The operator looking at this display replaces thetype wheel, operates the reset key to cancel the display of thepreceding message, and then returns to the text. It should be rememberedhere that changing the type wheel somewhere on a line of the text wouldcause the 1-line display 204 to indicate not only the characters beforethe cursor but those after the cursor in the new character patterns.

In the operations for displaying and printing the subsequent data input,use is made of the memory area II of the character pattern memory 224storing the special or scientific pattern data and the table II of theprint tables 216 storing the scientific control data.

When it is desired to replace the special type wheel with the originalstandard type wheel, one will depress the wheel change key K_(I) torepeat the procedure which has been generated by the initial depressionof the wheel change key K_(I) as previously stated.

The file prepared by the above procedure is sequentially stored in theouter storage device 208 of FIG. 1 one line at a time, as in theconventional word processor. A final document can be obtained from thecomplete file by transferring data from the outside storage device 5 tothe print buffer 212 via the data buffer 202 one line at a time. Thedata at the print buffer 212 is supplied to the printer 206 via theprint output control 214, which is generally referred to as "playback".In this instance, it is the second buffer area b that is initiallyloaded from the outer storage device 208 into the data buffer 202;nothing is loaded in the first buffer area a, that is, the cursor ispositioned at the head of the file.

Where the data is to be coupled to the printer 206, the data istransferred from the second buffer area b to the first a in accordancewith the continous movement of the cursor. When the control code WE₁ orWE₂ inputted during the previous text preparation has been detectedwhile data is transferred from the second buffer area b to the first a,the data buffer control 218 delivers a detection signal SC. This signalSC indicative of the coincidence between the cursor and the wheel changecontrol code is equivalent in function to the operation of the wheelchange key K_(I) or K_(II). The output SG₅ of the OR gate G₅ activatesthe latch and decoder 226 to generate a gate switch signal SA or SB and,at the same time, it is coupled to the data buffer control 218 as awheel change request. Then, the display 204 shows a message stored inthe message table 222 to indicate a change of type wheel and its kind.The detection signal SC is also fed from the data buffer control 218 toa printer control section (not shown) thereby immediately interruptingthe operation of the printer.

Suppose that the wheel change control code WE₁ has been entereddesignating the standard type wheel during the previously discussedpreparation of text data and before the entry of text data DT'. Then,the latch and decoder 226 delivers a logical "1" gate switch signal SAin response to a detection signal SC, which makes effective the table Istoring the control data of the standard type wheel and the memory areaI of the character pattern memory 224 storing the pattern data whichcorresponds to the standard type wheel. At the same time, the content ofthe message table 222 is fed to the display buffer 220 causing thedisplay 204 to display "WHEEL CHANGE : STANDARD". One, based on thisindication, confirms the kind of the type wheel and, if it is not thestandard one, replaces it. Thereafter, he manipulates the reset key tocancel the message on the display 204 and start a printing operation.

When the wheel change control code WE₂ has been detected during theprinting operation, the latch and decoder 226 renders the gate switchsignal SB logical "1" and the preceding signal SA logical "0". In thissituation, the table II and memory area II each storing the control datafor scientific applications are made effective. Simultaneously, themessage table 222 supplies data indicating a change of the type wheel tothe special one so that the display 204 indicates the message "WHEELCHANGE : SCIENTIFIC". Then, the operator replaces the type wheel withthe one for scientific applications, operates the reset key to cancelthe message on the display 204 and resumes the printing operation.

It will be seen from the above that the second embodiment described sofar with reference to FIGS. 12 and 13 promotes the use of not only astandard font but various special fonts such as for scientificexpressions for a printer while a document is prepared. The kind of atype wheel to be loaded in the carriage is indicated on a display so asto facilitate replacement. In the event of preparation of a finaldocument, not only the printer is stopped but the kind of a type wheelused for preparing the file is indicated on the display. This will allowthe type wheel to be changed quickly yet positively even though theoperator may have alternated with another or a long period may havelapsed after the preparation of the file. Additionally, such advantagesare achievable with a simple circuit arrangement which affords anotheradvantage in cost.

Various modifications will become possible for those skilled in the artafter receiving the teachings of the present disclosure withoutdeparting from the scope thereof. For example, the number of kinds oftype wheels available for the printer is not limited to two, as has beenemployed for the second embodiment, but may be three or more if desired.Such an increase in the number of type wheels should be accompanied bycorresponding increases in the wheel change keys, print tables 216,character pattern memories 224, print tables 216, character patternmemories 224, gates G₁ -G₄, gate switch signals delivered from the latchand decoder 226, messages stored in the message table 222, etc. The wordprocessor is not limited to one using alphanumeric characters but may bereplaced by one using any other kind of characters. The 1-line displayused for the word processor shown in FIG. 12 may be substituted for by acathode ray tube or like display means. Thus, it will be seen that thepresent invention is applicable to every possible type of word processorfurnished with printers which employ type wheels.

I claim:
 1. A control apparatus for a proportional spacing printerconstructed to selectively print with first and second fonts comprisinga common set of characters, widths of at least some characters in thefirst font differing from widths of respective characters in the secondfont, comprising:read-only storage means for pre-storing firstproportional space data for the first font; read-write storage means forstoring second proportional space data for the second font; buffer meansfor temporarily storing character codes corresponding to said charactersrespectively and the second proportional space data input thereto;discrimination means operatively connected to the buffer means fordiscriminating the character codes from the second proportional spacedata; transfer means operatively connected to the buffer means anddiscrimination means for transfering the second proportional space datadiscriminated by the discrimination means from the buffer means to theread-write storage means; and control means for controlling the printerto perform proportional printing with the first font using the firstproportional space data stored in the read-only storage means and toperform proportional printing with the second font using the secondproportional space data stored in the read-write storage means; thetransfer means being further operatively connected to the read-onlystorage means for initially transferring the first proportional spacedata from the read-only storage means to the read-write storage means,the transfer means subsequently transferring the second proportionalspace data from the buffer means to the read-write storage means toreplace respective data in the read-write storage means, the secondproportional space data comprising data for only those characters of thesecond font having widths differing from widths of respective charactersin the first font.
 2. A printer as in claim 1, in which the printer is ahammer type impact printer, the read-only storage means further storinghammer pressure data.
 3. A printer as claimed in claim 2, in which theread-write storage means further stores hammer pressure data.
 4. Aprinter as claimed in claim 10, in which the second proportional spacedata for each character comprises:a code for discriminating the secondproportional space data from the character codes; a code designatingsaid character; a proportional space value for said character; and acode designating the end of the second proportional space data for saidcharacter.